P1, P4-Di(uridine 5′)-tetraphosphate is a dinucleotide of the following structure: 
The free acid of P1, P4-di(uridine 5′)-tetraphosphate, where X is hydrogen, has been previously described as uridine 5′-(pentahydrogen tetraphosphate), P′″→5′-ester with uridine (CAS Registry Number: 59985-21-6; C. Vallejo et al., Biochimica et Biophysica Acta 438, 305 (1976) and H. Coste et al., J. Biol. Chem. 262, 12096 (1987)).
Different methods have been described for the synthesis of purine dinucleotides such as diadenosine tetraphosphate (A2P4) (E. Rappaport et al, Proc. Natl. Acad. Sci, 78, 838, (1981); A. Guranowski et al, Biochemistry, 27, 2959, (1988); C. Lobaton et al, Eur. J. Biochem., 50, 495, 1975; K. Ng and L. Orgel, Nucl. Acid Res., 15, 3573, (1987)). However, this has not been true for U2P4 which is a pyrimidine nucleotide. Although purine nucleotides and pyrimidine nucleotides appear to be analogous, the methods used for purine nucleotide synthesis do not necessarily work for pyrimidines such as uridine.
Several references describe protocols for the production of diuridine tetraphosphate. The methods described in the literature are very time consuming, lasting over five days and producing only small amounts of diuridine tetraphosphate (C. Vallejo et al., Biochimica et Biophysica Acta 438, 305 (1976), Sillero et al., Eur J Biochem 76, 332 (1972)). According to this technique, diuridine tetraphosphate was synthesized through a reaction of uridine 5′-monophosphomorpholidate with the triethylamine salt of pyrophosphoric acid in a medium of anhydrous pyridine. After 5 days at 30° C., pyridine was removed from the reaction mixture by evaporation, and the residue resuspended in glass-distilled water, the suspension applied to a DEAE-cellulose column and fractionated with a linear gradient (0.06-0.25 M) of ammonium bicarbonate, pH 8.6. The peak eluting between 0.17-0.19 M ammonium bicarbonate was partially characterized as U2P4 by the following criteria: insensitivity to alkaline phosphatase, phosphorus to base ratio and analysis of the products of hydrolysis (UTP+UMP), after treatment with phosphodiesterase I, by electrophoresis in citrate buffer, pH 5.0. No yield or spectroscopic data were given. Thus, these procedures for the synthesis of diuridine tetraphosphate are lengthy and produce only small amounts of only partially characterized diuridine tetraphosphate.
Diuridine tetraphosphate has been shown to have beneficial properties in the treatment of various diseases, such as chronic obstructive pulmonary disease (COPD). For example, it has been demonstrated to facilitate the clearance of mucous secretions from the lungs of a subject such as a mammal including humans in need of treatment for various reasons, including cystic fibrosis, chronic bronchitis, asthma, bronchiectasis, post-operative mucous retention, pneumonia, primary ciliary dyskinesia (M. J. Stutts, III, et al, U.S. Pat. No. 5,635,160; PCT International Publication WO 96/40059) and the prevention and treatment of pneumonia in immobilized patients (K. M. Jacobus and H. J. Leighton, U.S. Pat. No. 5,763,447). Further therapeutic uses include treatment of sinusitis (U.S. Pat. Nos. 5,789,391; 5,972,904; 5,981,506; 5,958,897; and PCT International Publication WO 98/03177), otitis media (U.S. Pat. No. 6,423,694; PCT International Publication WO 97/29756), dry eye (U.S. Pat. No. 5,900,407; PCT International Publication WO 98/34593), retinal detachment (PCT International Publication WO 02/060454), nasolacrimal duct obstruction (Publication No. US-2002-0103157-A1), the treatment of female infertility and irritation due to vaginal dryness via increased mucus secretions and hydration of the epithelial surface (U.S. Pat. No. 6,462,028; PCT International Publication WO 00/30629), and enhancing the performance of athletes.